Electricity control techniques for inverters are known in the art. U.S. Pat. No. 6,791,239 proposed by the Applicant is such an example. That technique focuses on the conventional inverter circuit and includes an individual pulse-width modulation (PWM) control unit, a driving unit, and a voltage boosting unit to drive an individual discharge lamp (CCFL or EEFL). As the size of display panels increases gradually, the number of the discharge lamps also increases. The required electricity increases too. Hence the size of circuit board to accommodate the configuration of the PWM control unit, driving unit and voltage boosting unit made according to the number of discharge lamps is larger, and circuit layout and production are more difficult. Illumination and electric field interference among the discharge lamps also increases. As a result, luminance uniformity suffers. While the aforesaid technique provides a solution, it mainly aims to provide, through a single PWM control unit, synchronous driving signals of the same phase and same frequency according to the driving units and voltage boosting units that are required to drive the discharge lamps on the rear end. Thereby each driving unit, voltage boosting unit and discharge lamp can be driven synchronously to achieve the uniform luminance.
U.S. Pat. No. 6,867,955 and U.S. Patent Publication No. 2005/0122066 A1 disclose other techniques to address the arc discharge phenomenon occurred to an inverter at a high voltage output zone in abnormal conditions. They provide a protection device which generates a protection signal which is fed back to a control unit to stop high voltage output in the high voltage zone.
However, with the size of the display panel increased constantly, the number of the discharge lamps increases even more. The driving lines for the driving units, voltage boosting units and discharge lamps also increase. If one of the lines is abnormal (not necessary malfunctions, could be an irregular voltage for a short period of time), the control unit receives the signal and stops all driving signals. If this situation occurs to the upper discharge lamps where heat concentrates, the display panel will be shut down and cannot display. Moreover, as the display panel becomes larger, if merely one discharge lamp is abnormal, it does not seriously effect user's viewing of the display panel. Hence the existing techniques that provide a single protection control mode are troublesome and undesirable.